Field-of-view controlling arrangements

ABSTRACT

A field-of-view controlling arrangement such as a privacy screen includes a single microprism or lenticular sheet having a plurality of sets of parallel surfaces that intersect to form prisms or lenticular structures, and in which field-of-view control is achieved by (i) for sheets made up of parallel “one-dimensional” microprism or lenticular structures having at least two intersecting sets of mutually parallel surfaces, altering at least two sets of the mutually parallel surfaces, and/or portions of the at least two sets of mutually parallel surfaces, by applying a light-attenuating treatment, (ii) for sheets made up of polyhedral lenticular structures having at least three intersecting sets of mutually parallel surfaces, or at least one set of curved surfaces extending in directions transverse to directions in which the field-of-view is to be limited, altering at least one set of the mutually parallel or curved surfaces by applying a light-attenuating treatment, or (iii) for any type of microprism or lenticular sheet, including a diffusing agent in at least a portion of the sheet, and arranging the surfaces of the microprism or lenticular sheet so that light transmitted along selected optical paths is attenuated before exiting the sheet.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to field-of-view controlling arrangements,such as privacy screens, made up of microprism or lenticular sheets.

[0003] More particularly, the invention relates to a field-of-viewcontrolling arrangement made up of a microprism or lenticular sheethaving a plurality of sets of parallel surfaces that intersect to formprisms or lenticular structures, and in which field-of-view control orprivacy screening is achieved by:

[0004] for sheets made up of parallel “one-dimensional” microprism orlenticular structures having at least two intersecting sets of mutuallyparallel surfaces, altering a first set of mutually parallel surfacesand at least one second set of the mutually parallel surfaces of themicroprism or lenticular structures, and/or portions of the at least twosets of mutually parallel surfaces, by applying a light-attenuatingtreatment to the surfaces,

[0005] for sheets made up of “two-dimensional” or polyhedral lenticularstructures having at least three intersecting sets of mutually parallelsurfaces, or at least one set of curved surfaces extending in directionstransverse to directions in which the field-of-view is to be limited,altering at least one set of the mutually parallel or curved surfaces byapplying a light-attenuating treatment to the at least one set ofmutually parallel or curved surfaces, and

[0006] for any type of microprism or lenticular sheet, including adiffusing agent in at least a portion of the sheet, and arranging thesurfaces of the microprism or lenticular sheet so that light transmittedalong selected optical paths is attenuated before exiting the sheetthrough a first set of surfaces while light transmitted along otheroptical paths is relatively unattenuated before exiting the sheetthrough a second set of surfaces oriented at a nonzero angle relative toeach of the surfaces in the first set of surfaces,

[0007] thereby achieving a privacy screen that restricts viewing of animage from more than one side of the potential field-of-view.

[0008] The privacy screens of the invention represent an improvementover the privacy screens disclosed in copending U.S. patent applicationSer. No. 09/583,731, filed Mar. 30, 2000, and Ser. No. 09/481,942, filedJan. 13, 2000, (both incorporated herein by reference), which discloseprivacy screens in which privacy screening is achieved by altering justone set of mutually parallel surfaces or facets of a conventionalmicroprism sheet of the type having a single set of “one-dimensional”prisms, i.e., prisms formed by parallel grooves in the sheet, toattenuate light so as to restrict the field-of-view, for imagestransmitted by the sheet, to only one side of the field-of-view.

[0009] The privacy screens of the invention may be used as overlays forvideo displays, for example to restrict eavesdropping with respect to acomputer display, or as window coverings. When used as window coverings,the privacy screens of the invention have the additional advantage thatthe prisms or lenticular structures that make up the screen may be usedto bend incoming light and improve the view from the window. Inaddition, the privacy screens or the invention may, at desired angles,include embedded images or graphics, and may provide other screeningfunctions such as attenuation of ultra-violet light or other radiation,polarization, and so forth.

[0010] 2. Description of Related Art

[0011] As illustrated in FIG. 1, the privacy screen disclosed incopending U.S. patent application Ser. No. 09/481,942 is made up of amicroprism sheet 1 having multiple sets of parallel surfaces 3,4 thatintersect to form prisms defined by adjacent parallel grooves 2.

[0012] In order to provide a privacy screening effect, one set of theparallel surfaces 3 is altered by surface treatment to attenuate orscatter transmitted light in selected directions. The result of thisarrangement is a simple and inexpensive privacy screen that permitsviewing of an image by an observer 25 through the untreated set ofsurfaces 4, and that prevents viewing of the image through the treatedsets of surfaces 3, the angles α and β of the respective surfacesdetermining the range of angles in which viewing is restricted. Uses forthe privacy screen described in copending application Ser. No.09/481,942 include computer monitor overlays that prevent eavesdropping,stereoscopic viewing devices, and two-player video game arrangementssuch as the one illustrated in FIG. 3, in winch an overlay 12 consistingof multiple sheets 6 and 7 is used to restrict viewing by the respectivecame players of opposite portions of an image displayed on screen 13.

[0013] Although the privacy screen described in U.S. patent applicationSer. No. 09/481,942 is ideally suited to applications such as the oneillustrated in FIG. 3, in which only one side of the field-of-view of animage needs to be restricted, applications such as eavesdroppingprevention often call for restriction of viewing from at least twosides. Furthermore, it would be desirable if additional optical effectscould be achieved with a single sheet, even if viewing from only oneside need be restricted.

[0014] One solution to the problem of limiting viewing from more thanone side of the field-of-view is proposed in the above-cited U.S. patentapplication Ser. No. 09/583,731. According to this solution, privacyscreens identical to those described in U.S. patent application Ser. No.09/481,942 are stacked with the treated sets of surfaces oriented indifferent directions to restrict the field-of-view of an image frommultiple sides. While this solution is simple and effective, the presentinvention proposes two even simpler solutions, both involving use of asingle rather than multiple microprism or lenticular sheets.

[0015] The two alternative solutions respectively involve use of surfacetreatment and bulk diffusion materials, and are discussed separatelybelow.

[0016] Surface Treatment

[0017] The first alternative solution to the problem of restricting thefield-of-view of an image from multiple sides is to use surfacetreatments similar to those described in the above-discussed U.S. patentapplication Ser. Nos. 09/481,942 and 09/583,731. However, instead ofaltering a single set of parallel surfaces or facets of a the microprismsheet to attenuate light so as to narrow the field-of-view of imagespassing through the sheet, the present invention proposes to achieveprivacy screening by altering at least two of the sets of mutuallyparallel surfaces, portions of the at least two sets of mutuallyparallel surfaces, or a corresponding set of identically oriented curvedsurfaces, and in particular by applying a light attenuating surfacetreatment to the sets of mutually parallel or curved surfaces. Theresult of such treatment or multiple sets of surfaces is a privacyscreen that restricts viewing of an image from more than one side of thepotential field-of-view without the need to stack multiple sheets.

[0018] As discussed in detail in U.S. patent application Ser. No.09/481,942, it is of course well-known in general to selectively treatsurfaces of a microprism or lenticular structure for the purpose ofselectively attenuating light passing through the sheet. However, suchtreatments had always been, prior to development of the privacy screendisclosed in U.S. patent application Ser. No. 09/481,942, used in a waythat attenuates or scatters background light, rather than the imageitself, so as to reduce glare or increase image visibility, contrast, orrelative brightness. Furthermore, the prior microprism or lenticularstructures had always been combined with other structures to form a rearor front projection screen, rather than being used as a stand-alonesheet or overlay used solely or the purpose of privacy screening.

[0019] The numerous prior patents disclosing treatment of microprism orlenticular surfaces to attenuate or re-direct background light forpurposes of glare reduction, brightness and contrast optimization, orthe like, thus tend to teach away from the invention, which involvesintentional attenuation of the image itself, in certain directions.Nevertheless, it should be noted that the same surface treatmentsdisclosed in the prior patents may also be used in connection with thepresent invention, albeit on different surfaces of the sheets.Potentially useful surface treatment techniques include various coatingprocesses such as printing, vapor deposition, or sputtering of opaque orlight-scattering materials, delustering, chemical or laser etching,casting, and differential polishing of previously roughened surfaces.

[0020] Many of these techniques are disclosed in the following patentsdirected to microprism sheets in general:

[0021] U.S. Pat. No. 5,836,096 (Brauer), U.S. Pat. No. 5,512,219(Rowland et al.) U.S. Pat. No. 5,446,594 (Nelson et al.), U.S. Pat. No.5,363,237 (Wakatake), U.S. Pat. No. 5,316,359 (Lansinger), U.S. Pat. No.5,208,620 (Mitsutake et al.), U.S. Pat. No. 4,708,435 (Yata et al.),U.S. Pat. No. 4,309,074 (Granieri), U.S. Pat. No. 4,309,073 (Nishimuraet al.), U.S. Pat. No. 4,206,969 (Cobb et al.), U.S. Pat. No. 3,971,051(Baker et al.), U.S. Pat. No. 3,902,787 (Sherlock), and U.S. Pat. No.3,718,078 (Plummer),

[0022] as well as in the following patents directed to glare reductionscreens having a single treated surface arranged generally parallel tothe direction of image transmission, thereby effects of backgroundlight:

[0023] U.S. Pat. No. 4,911,529 (Van De Ven), U.S. Pat. No. 4,756,603(Ohtani), U.S. Pat. No. 4,165,920 (Brown), U.S. Pat. No. 2,909,770(Pugsley), in the following patents that disclose use of lenticular ormicroprism sneets as isotropic light diffusers in rear projectionsystems:

[0024] U.S. Pat. No. 4,730,897 (McKechnie et al.), U.S. Pat. No.5,400,114 (Yoshida et al.), U.S. Pat. No. 5,457,572 (Ishii et al.), U.S.Pat. No. 5,581,407 (Mitani et al.), U.S. Pat. No. 5,760,955 (Goldenberget al.), U.S. Pat. No. 6,002,829 (Winston et al.), U.S. Pat. No.6,157,491 (Watanabe et al.), U.S. Pat. No. 6,025,897 (Weber et al.), andU.S. Pat. No. 6,169,633 (Watanabe), and

[0025] in the following patents directed to use of microprism orlenticular sheets to increase the field of view in non-projection ordirect sight type LCD systems:

[0026] U.S. Pat. Nos. 5,745,199 and 5,555,476, both to Suzuki et al.

[0027] These and other patents offer guidance on altering the propertiesof optical surfaces, though not for the purposes of the presentinvention.

[0028] Bulk Diffusion

[0029] This alternative solution to the problem of achieving privacyscreening from more than one side using a single microprism orlenticular sheet involves including a diffusing agent in at least aportion or section of the sheet, and arranging surfaces of themicroprism or lenticular sheet so that light along selected opticalpaths is attenuated before reacting the surfaces.

[0030] The use of diffusing materials for what may be thought of as“collimation” should not be confused with the use of diffusing materialsfor collimation in arrangements such as the one disclosed in U.S. Pat.No. 5,837,346 (Langille et al.). In he arrangement disclosed in U.S.Pat. No. 5,837,346, a combination of bulk diffusion and surfacetexturing is used to achieve the same effect as a Fresnel lens, i.e.,causing light incident on the rear of the screen at a wide range ofangles to exit the front of the screen in parallel. Although one effectof the present invention is also to achieve “collimation” (in thebroadest sense of the word) of the transmitted image, the “collimation”provided by the multiple zone privacy screen of the invention, i.e.,attenuation rather than focusing of light incident at non-parallelangles, is not to be confused with the type of collimationconventionally provided in rear projection screens. Whereas the presentinvention seeks to narrow the field-of-view of an image and prevent theimage, or portions of an image, from being viewed at angles outside adesired range, collimators of the type used in rear projection screensseek to concentrate the light without attenuation. This may beaccomplished solely by using Fresnel lens structures, with no need forany sort of diffuser, but it can also be achieved, at least according toU.S. Pat. No. 5,837,346, by combining bulk diffusion with surfacetexturing to impart asymmetrical diffusion characteristics to thescreen.

[0031] Thus, while the present invention shares with the projectionscreen described in U.S. Pat. No. 5,837,346, an embodiment that alsohappens to use bulk diffusion, the functions of the respective diffusionmaterials differ substantially. The prior collimating diffusionstructure seeks to provide a collimating lens effect in which lightincident at a wide range of angles exits the screen at a narrower rangeof angles, while the diffusion structure of the present invention simplyseeks to attenuate all light incident on the screen that is outside thenarrower range of angles.

[0032] One reason for the substantial difference in function between“collimating” structures of the type disclosed U.S. Pat. No. 5,837,346and that of the present invention, is essentially that rear projectioncollimation of the type disclosed in U.S. Pat. No. 5,837,346 requiresthat the bulk diffusion material have asymmetric or anisotropicdiffusion characteristics, whereas the corresponding bulk diffusionmaterials of the present invention may diffuse light isotropically(although anisotropic diffusion may also work), the privacy screeningeffect being achieved not by differences in scattering patterns, but inthe lengths of the paths through which light traverses the material,resulting in an especially simple privacy screen construction thatnevertheless achieves privacy screening on at least two sides of animage.

SUMMARY OF THE INVENTION

[0033] It is accordingly a first objective of the invention to provide amore versatile field-of-view controlling arrangement in which thefield-of-view may be controlled or restricted from any side over anyrange of angles, including from multiple sides.

[0034] It is a second objective of the invention to provide afield-of-view controlling arrangement that can be used not only torestrict the field-of-view from one or more sides, but also to improveor modify images visible in the unrestricted portion of thefield-of-view.

[0035] It is a third objective of the invention to provide an improvedprivacy screen that restricts the field-of-view of an image from atleast two sides, and yet that consists of a single microprism orlenticular sheet.

[0036] It is a fourth objective of the invention to extend the range ofapplications for the microprism or lenticular privacy screens disclosedin U.S. patent application Ser. Nos. 09/481,342 and 09/583,732 toapplications that require multiple privacy zones, without significantlyincreasing cost or difficulty of manufacture.

[0037] It is a fifth objective of the invention to provide a privacyscreen that is suitable for use with lenticular as well as microprismsheets, the lenticular sheets offering additional possibilities of imagemodification or enhancement, including image magnification, while stillproviding privacy screening effects using a single sheet.

[0038] It is a sixth objective of the invention to provide privacyscreens having increased versatility and yet that are simple tomanufacture and that can easily be adapted for use in a variety ofcontexts.

[0039] It is a seventh objective of the invention to provide privacyscreens suitable for use as a computer monitor or television overlay,and which limits viewing of a displayed image to persons situated at aspecific range of angles relative to the monitor or television.

[0040] It is a eighth objective of the invention to provide privacyscreens that may be applied to a window, and which not only serve as ablind, but also can be arranged to improve the view through the window,and/or to replace an undesired view with images or graphics.

[0041] These objectives are achieved by:

[0042] in accordance with the principles of a first preferred embodimentof the invention, altering at least two sets of mutually parallelsurfaces of a microprism or lenticular sheet and a second set ofmutually parallel surfaces of a microprism or lenticular sheet that areoriented at different angles relative to a principal plane of the sheet,and/or portions of the two sets of mutually parallel surfaces, so as toattenuate light on selected sides of the field-of-view for an imagetransmitted through the sheet by applying a light attenuating surfacetreatment to the surfaces, or

[0043] also in accordance with the principles of the first preferredembodiment of the invention, altering at least one set of mutuallyparallel surfaces, or corresponding curved surfaces, of a microprism orlenticular sheet in which the microprisms or lenticular elements areformed by polyhedra or other discrete structures such as frustoconicallenticules, and

[0044] alternatively, in accordance with the principles of a secondpreferred embodiment of the invention, including a diffusing agent inthe material of the sheet, and arranging selected surfaces of themicroprism or lenticular sheet so that light along selected opticalpaths is attenuated before exiting the selected surfaces.

[0045] Each of the two preferred embodiments of the invention provides aprivacy screen that can be adapted to restrict viewing of an image fromat least one or two sides of the potential field-of-view, with someimplementations offering the possibility of restricting viewing fromthree sides, and of achieving additional optical effects such asexpansion of the field-of-view in the unrestricted directions.Furthermore, the privacy screen of each of the two preferred embodimentsof the invention is made of a single sheet which can be arranged toserve as a very simple screen overlay to prevent observers situated ondifferent sides of the screen from eavesdropping.

[0046] In one implementation of the first preferred embodiment of theinvention, the above-described surface treatment principles may beapplied to a conventional microprism sheet of the type described in U.S.patent application Ser. No. 09/481,942, i.e., a microprism sheet havinga plurality of v-shaped grooves forming two sets of parallel surfacesthat intersect to form grooves, by surface treating both surfaces ofalternate ones of the grooves.

[0047] In other implementations of the first preferred embodiment of theinvention, the microprism sheets may include truncated prism structuresformed by spacing apart the v-shaped grooves, lenticular sheets havingv-shaped grooves and one or two-dimensional lens structures, and sheetswith grooves on opposite sides of the sheet, either aligned oralternating, and either spaced-apart (to form truncated prismstructures) or adjacent (to form v-shaped prism structures).

[0048] In still further implementations of the first preferredembodiment of the invention, the sheets to which the surface treatmentsare applied are polyhedral structures, which may include truncatedtetrahedral lenticular structures, tetrahedral structures, othermultifaceted or polyhedral lenticular structures, and frustoconical orsimilar structures, and in which light-attenuating surface treatmentsare applied to at least one of the mutually parallel or curved sets ofsurfaces that form the discrete lenticular structures.

[0049] The surface treatments applied may consist of any surfacetreatments that have the effect of absorbing or scattering light andthat can be applied to selected surfaces by means of a mask, control ofthe surface treatment tool, or use of an appropriate die, includingapplication of opaque or light diffusing coatings, delustering, chemicalor laser etching, casting, and differential polishing of previouslyroughened surfaces, as well as any other surface treatment methodsdescribed in the above-cited patents or patent applications, or that areknown or may become known to those skilled in the art. Further, as anthe privacy screens of the above-cited applications, it is alsopossible, in addition to surface treatments that merely block or scatterlight, to add surface treatments result in the appearance of images orgraphics at selected angles.

[0050] With respect to the second preferred embodiment of the invention,rather than forming a privacy screen by preventing viewing of an imagein the direction of treated surfaces and permitting viewing of the imagethrough the untreated surface (or vice versa), the same effect can beachieved by forming the microprism or lenticular sheet using a bulkdiffuser in at least a portion or section of the sheet, the diffuserbeing preferably concentrated if not evenly distributed) in the portionor section of the sheet adjacent the light entrance side. In contrast toprojection screen diffusers, which seek to collimate light by causing itto bend towards a preferred diffusion axis, the diffuser of theinvention should be arranged so that the diffusion effect depends solelyon the amount of diffusing material that must be traversed by aparticular ray of the image transmitted by the sheet. Although thematerial of the bulk diffuser may be isotropic, it will be appreciatedthat anisotropic materials may also be utilized so long as theanisotropy causes greater attenuation in the direction of desiredprivacy than in the viewing direction,

[0051] In the embodiment in which the sheet is made up of parallelv-shaped grooves, the dimensions of the grooves and sheet may generallybe the same as those described in copending U.S. patent application Ser.No. 09/481,581, although the invention is not limited to particulargroove dimensions. As explained in the parent application, grooveshaving a pitch on the order 0.12 to 0.14 inches are undiscernable by aperson having normal vision at a typical distance from a screen, andthus may be appropriate for the privacy screening structure of theinvention. Depending on the shapes of the prisms and the locations ofthe coatings, it may also be necessary to reduce the pitch and size ofthe grooves in order prevent the viewer from perceiving Moiré effectsresulting from the contrast between the treated and untreated portionsof the sheet.

[0052] Also as in the aforementioned patent applications, and especiallyU.S. patent application Ser. No. 09/583,731, the configuration of themicroprism or lenticular sheet may itself be varied by, for example,varying the pitch, shapes, or sizes of the grooves, prisms, or lenses,or the thickness of the sheet, relative to the center or edges of thesheet, or by constructing the sheet as a curved rather than planarstructure.

[0053] Finally, while the privacy screens of the preferred embodimentsof the invention are especially suitable for use in restrictingeavesdropping by persons situated above or below a computer monitor ortelevision screen, the invention is not to be limited to a particularapplication. Instead, it is anticipated that the privacy screen of theinvention may be used in any of a variety of potential applications thatmight involve restricted viewing of an image or scene, includingapplications in which the privacy screens of the invention are appliedto windows to serve as blinds, and applications that involve restrictingviewing or more tan two sides of the image, or example by surfacetreating multiple sets of surfaces of a two-dimensional lenticularsheet, or by appropriate use of a bulk diffuser in such a sheet. Whenapplied to a window, the privacy screens of the invention not only canprovide privacy and restrict incoming light, but also can modify theview through the window by using the prisms or lenticular structures ofthe overlay to bend light is selected directions, or modify the view byadding images or graphics visible at selected angles.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054]FIG. 1 is an isometric view of a privacy screen of the typedisclosed in U.S. patent application Ser. No. 09/481,942.

[0055]FIG. 2 is a plan view, taken either from the top or side dependingon the orientation of the sheet, of the privacy screen illustrated inFIG. 1.

[0056]FIG. 3 is a perspective view of a screen overlay using privacyscreens of the type illustrated in FIGS. 1 and 2.

[0057]FIG. 4 is a plan view of a privacy, screen having multiple privacyzones constructed in accordance with the principles of a first preferredembodiment of he invention.

[0058]FIG. 5 is a plan view of a modification of the privacy screenillustrated in FIG. 4, in which tops of the prism structures aretruncated.

[0059]FIG. 6 is another modification of the privacy screen illustratedin FIG. 4, which includes a lenticular structure.

[0060]FIG. 7 is a plan view of yet another modification of the privacyscreen illustrated in FIG. 4, in which the privacy screen includesaligned, spaced, parallel grooves and lenticular structures on oppositesides of the sheet.

[0061]FIG. 8 is a plan view of a modification of the privacy screenillustrated in FIG. 4 in which only portions of the surfaces in each setof parallel surfaces are treated to attenuate or scatter light passingthrough, and in which the screen includes alternating parallel grooveson opposite sides of the sheet.

[0062]FIG. 9 is a plan view of a modification of the privacy screen ofFIG. 4, in which only portions of the surfaces of a structure otherwiseidentical to that of FIG. 4 are treated.

[0063]FIG. 10 is a plan view of a further modification of the privacyscreen of FIG. 4, in which only portions of the surfaces of themicroprism screen are treated, and in which the microprism sheetincludes aligned, adjacent parallel grooves.

[0064]FIG. 11 is a plan view of a privacy screen constructed inaccordance with the principles of a second preferred embodiment of theinvention, in which the privacy screen includes a bulk diffuser ratherthan surface treatments, the structure of the sheet otherwisecorresponding to that shown in FIG. 5.

[0065]FIG. 12 is a plan view of a privacy screen having, according tothe principles of the second preferred embodiment of the invention, abulk diffuser rather than surface treatment, but otherwise correspondingto the structure shown in FIG. 7.

[0066]FIG. 13 is a plan view of a privacy screen made up of a lenticularsheet with a bulk diffuser according to the principles of the secondpreferred embodiment of the invention.

[0067]FIG. 14 is a perspective view of a privacy screen made up of alenticular sheet including truncated tetrahedral structures arranged instaggered rows and having at least one treated set of mutually parallelsurfaces according to the principles of a variation of the firstpreferred embodiment of the invention.

[0068] FIGS. 15-18 are plan views of the lenticular sheet of FIG. 14, inwhich different surfaces are treated to control the viewing angle indifferent directions.

[0069]FIG. 19 is a perspective view of a privacy screen made up of alenticular sheet including truncated tetrahedral structures arranged ina grid pattern and having at least one treated set of mutually parallelsurfaces according to the principles of another variation of the firstpreferred embodiment of the invention.

[0070] FIGS. 20-23 are clan views of the lenticular sheet of FIG. 19, inwhich different surfaces are treated to control the viewing angle indifferent directions.

[0071]FIG. 24 is a perspective view of a privacy screen made up of alenticular sheet including tetrahedral structures arranged in staggeredrows and having at least one treated set of mutually parallel surfacesaccording to the principles of another variation of the first preferredembodiment of the invention.

[0072] FIGS. 25-28 are plan view of the lenticular sheet of FIG. 24, inwhich different surfaces are treated to control the viewing angle indifferent directions.

[0073]FIG. 29 is a perspective view of a privacy screen made up of alenticular sheet including truncated tetrahedral structures arranged ina grid pattern and having at least one treated set of mutually parallelsurfaces according to the principles of another variation of the firstpreferred embodiment of the invention.

[0074] FIGS. 30-33 are plan views of the lenticular sheet of FIG. 29, inwhich different surfaces are treated to control the viewing angle indifferent directions.

[0075]FIG. 34 is a perspective view of a privacy screen made up of alenticular sheet including truncated hexahedral structures arranged in ahoneycomb pattern and having at least one treated set of mutuallyparallel surfaces according to the principles or another variation ofthe first preferred embodiment of the invention.

[0076] FIGS. 35-44 are plan views of the lenticular sheet of FIG. 34, inwhich different surfaces are treated to control the viewing angle indifferent directions.

[0077]FIG. 45 is a perspective view of a privacy screen made up of alenticular sheet including tetrahedral structures arranged in ahoneycomb pattern and having at least one treated set of mutuallyparallel surfaces according to the principles of another variation ofthe first preferred embodiment of the invention.

[0078] FIGS. 46-55 are plan views of the lenticular sheet of FIG. 45, inwhich different surfaces are treated to control the viewing angle indifferent directions.

[0079]FIG. 56 is a perspective view of a privacy screen made up of alenticular sheet including frustoconical structures having a treatedsurface according to the principles of another variation of the firstpreferred embodiment of the invention.

[0080]FIG. 57 is a plan view of the lenticular sheet of FIG. 56.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0081] FIGS. 4-10 illustrate the principles of a version of a firstpreferred embodiment of the invention in which a field-or-viewcontrolling or privacy screening effect is achieved by altering at leasttwo sets of mutually parallel surfaces of a microprism or lenticularsheet, and/or portions of the two sets of mutually parallel surfaces,the two sets of surfaces being oriented at different angles relative toa principal plane of the sheet, so as to attenuate light in selecteddirections by applying a light attenuating surface treatment to thesurfaces. FIGS. 11-13 illustrate a second preferred embodiment of theinvention in which the microprism or lenticular sheet is made of a bulkdiffusing material and the surfaces of the sheet are arranged so thatlight transmitted along selected optical paths is attenuated beforeexiting the sheet through a first set of mutually parallel surfaceswhile light transmitted alone other optical paths is relativelyunattenuated before exiting the sheet through a second set of mutuallyparallel surfaces oriented at a nonzero angle relative to the first setof mutually parallel surfaces.

[0082] FIGS. 14-57 illustrate variations of the first preferredembodiment of the invention in which the microprism or lenticular sheetis made up of “two-dimensional” or discrete lenticular structures havingat least three intersecting sets of mutually parallel surfaces, or atleast one set of curved surfaces extending in directions transverse todirections in which the field-of-view is to be limited, and in which atleast one set of the mutually parallel or curved surfaces altered byapplying a light-attenuating treatment to the mutually parallel orcurved surfaces.

[0083] As explained above, each of the two preferred embodiments of theinvention provides a field-of-view controlling arrangement or privacyscreen that restricts viewing of an image from more than one side of thepotential field-of-view. Furthermore, the field-of-view controllingarrangement of each of the two preferred embodiments of the invention ismade of a single sheet, which can be arranged to serve as a very simplescreen overlay, for example to prevent observers from viewing a screenfrom both above the screen and below the screen. The dimensions of thesheets are essentially determined by the technology used to form thesheets and to treat the surfaces, although the pitch of the grooves orlenticular elements is Preferably made small enough to eliminateperception of the grooves or Lenticular elements, and/or Moiré patternsresulting from parallel arrangement of light transmitting and diffusingsurfaces. A pitch of less than ten grooves or elements per inch, andpreferably less than twenty grooves per inch, will provide the bestappearance most applications, although the invention is not in principlelimited to particular sheet dimensions or pitones.

[0084] Turning to the first preferred embodiment of the invention, ineach of FIGS. 4-10, the treated surfaces are represented by elements20,21, drawn as opaque or light-diffusing coatings having an exaggeratedthickness so that the principles of the first preferred embodiment maybe more readily understood. It is to be understood, however, that thesurface treatments applied may consist of any surface treatments thathave the effect of absorbing or scattering light and that can be appliedto selective surfaces by means of a mask, die, tool, or the like. Inaddition to coatings, possible surface treatments include delustering,chemical or laser etching, casting, and differential polishing ofpreviously roughened surfaces, as well as any other surface treatmentmethods described in the above-cited patents or patent applications, orthat are known or may become known to those skilled in the art. Forexample, if the surfaces are treated by printing, graphic images may beadded so that the blocked image or scene is replaced by a graphic image.

[0085] Also in each of FIGS. 4-10, the untreated surfaces arerepresented by surfaces 24,25. Although referred to as “untreated,”however, it is to be understood that surfaces 24,25 may in fact betreated to enhance transmission of light through the surfaces, forexample by polishing, curing, adding transparent protective coatings,and or printing of portions of the surfaces so as to superimpose graphicimages on the images being viewed through the screen. The term“untreated” is intended to mean “not altered to diffuse or attenuatelight.”

[0086] Turning to specific implementations of the first preferredembodiment of the invention, FIG. 4 illustrates an arrangement in whichthe above-described surface treatment is applied to a conventionalmicroprism sheet of the type described in U.S. patent application Ser.No. 09/481,942, i.e., a microprism sheet having a plurality of groovesdefined by two intersecting sets of surfaces. In this implementation ofthe first preferred embodiment, the privacy screening effect is obtainedby surface treating both surfaces 20,21 of alternate grooves to create alouver, so that rays 22 at a first range of angles A and rays 23 at asecond range of angles B are selectively attenuated or blocked.

[0087] In the implementation illustrated in FIG. 5, the standardmicroprism sheet illustrated in FIG. 4 is modified by spacing thegrooves to form truncated prism structures, which has the advantage thatall parallel surfaces in the sheet may be coated, rather than alternateparallel surfaces as in the embodiment of FIG. 4. This should have theeffect of simplifying manufacture of the screen without adverselyaffecting its optical properties, the angles of the privacy zonescreated by treated surfaces 20,21 being the same in this implementationas in the implementation of FIG. 4.

[0088] In the implementation illustrated in FIG. 6, the sheet includesuntreated lenticular elements 26. Again, as in implementation of FIG. 5,the treated surfaces 20,21 constitute all parallel groove-definingsurfaces on one side of the sheet, enabling simplified manufacture ofthe privacy screen. The use of lenticular elements 26 permits opticaleffects to be added to the privacy screening effect. For the illustratedsemi-cylindrical lenticular elements, the optical effect obtained ismagnification of the image, although it will be appreciated that othereffects could be obtained by varying the shape of the lenticularelements. The lenticular elements may, for example, include conventionalone or two dimensional lenticular elements (i.e., barrel shaped orhemispherical lenses), and lens structures having concavities or otherdepartures from the illustrated structures.

[0089] The implementation illustrated in FIG. 7 also involves lenticularstructures 26, but in order to further extend the image modificationcapabilities of the lenticular structures, includes parallel,spaced-apart grooves on both sides of the microprism sheet, enablinginclusion of the lenticular structures 26 on either or both sides of thesheet. In the illustrated implementation, the lenticular structures 26may, depending on their exact shape, be used for such purposes as imagecompression, modification, or special effects.

[0090] The implementations illustrated in FIGS. 8-10 involve partialtreatment of surfaces of the various sheets. While achieving treatmentof portions of the groove surfaces would appear to be technically moredifficult than treatment of complete surfaces, such partial treatmentpermits the use of accordion-shaped sheets, i.e., sheets withalternating grooves on opposite sides of the sheet, as illustrated inFIG. 8, and/or enables treatment of each groove rather than alternatinggrooves without having to space the grooves apart (or truncate theprisms), as can be seen by comparing FIG. 9 with FIG. 4 and FIG. 10 withFIG. 7.

[0091] According to the variation of the first preferred embodimentillustrated in FIGS. 14-18, the field-of-view controlling arrangement ismade up of a lenticular sheet that include staggered rows of lenticularelements in the form or truncated tetrahedral structures 100 having fivesets of mutually parallel surfaces indicated by reference numerals101-105. According to the principles of this embodiment of theinvention, any one or more of surfaces 101-105 may be selectivelytreated to provide a privacy screening effects, the range of angles ofwhich is determined by the orientations of the treated surfaces in amanner similar to the that of the privacy screens illustrated in FIGS.1-10. For example, in the arrangement of FIG. 15, only surface 101 istreated, while in the arrangements of FIGS. 16-18, surfaces 101 and 105;101, 104, and 105; and 101 and 104 are respectively subjected to alight-attenuating surface treatment in the manner described above withrespect to FIGS. 1-10.

[0092] FIGS. 19-23 illustrate a field-of-view controlling arrangementsimilar to that of FIGS. 14-18 except that the truncated tetrahedrallenticular elements 200 are arranged in a grid rather than in staggeredrows. Again, any one or more of the surfaces 201-205 may be subjected toa light-attenuating surface treatment in the manner described above.

[0093] FIGS. 24-33 illustrate further variations of the field-of-viewcontrolling arrangements of the first preferred embodiment in which thelenticular elements are non-truncated tetrahedral structures (300,400)in staggered rows FIGS. 4-28) or non-staggered rows (FIGS. 29-33) and inwhich any set of surfaces 301-304,401-404 may be subjected to a lightattenuating surface treatment, while FIGS. 34-55 show correspondingarrangements of truncated or non-truncated hexahedral structures 500,600forming a honeycomb pattern and in which any of surfaces 501-507,601-606are treated to create privacy screening effect.

[0094] Finally, FIGS. 56 and 57 show a variation of the first preferredembodiment of the invention in which the lenticular elements arefrustoconical-shaped structures 700 having surfaces 701 and 702 in whichthe curved surface 701 which forms sides of the structure is providedwith a light-attenuating surface treatment to provide a 360° privacyscreening effect.

[0095] One advantage of in using staggered rows or a honeycomb patternof lenticular elements is that it reduces the so-called “staircase”effect, which results in distortion or blurring of non-horizontal orvertical lines, caused by the quantum or discrete nature of alignedmicroprism or Tentacular elements. In addition, non-truncated discreteelements have the advantage of providing maximal glare reduction anexpansion of the field-of-view in non-restricted directions.

[0096] It will of course be appreciated by those skilled in the art thatthe different discrete lenticular structures illustrated in FIG. 14-57represent only a few of the possible geometric shaves that could beadapted to provide a field-of-view controlling or privacy screeningeffect according to the principles of the first preferred embodiment ofthe invention, and that the invention is not to be limited to theparticular shapes illustrated.

[0097] In the specific implementations of the second preferredembodiment of the invention illustrated in FIGS. 11-13, a bulk diffuseris added to sheets having shapes corresponding to those illustrated inFIGS. 5, 7, and 6, respectively. Because the optical paths 30,31 throughthe diffusing material differ as a result of the orientation of the exitsurfaces 32,33, light transmitted along optical paths 30 will beattenuated more than light transmitted along optical paths 31, resultingin a privacy screening effect.

[0098] Although some differential attenuation will occur even if thebulk diffuser is even distributed throughout the sheet, the greatestdifference in optical paths through the diffusing material will occur ifthe diffusing material is concentrated at the rear of the sheet, i.e.,on the light entrance side, with the front of the sheet being relativelytransparent. This is illustrated in FIGS. 11-13 by including separatereference numerals 33 and 34 for respective zones of greater and lesserconcentration of diffusing material.

[0099] In the arrangement illustrated in FIG. 14, sections 34 arepreferably completely transparent in order to optimize the opticaleffects provided by the use of lenticular elements 35. Alternatively, inany of the implementations illustrated in FIGS. 11-13, it is possible toenhance the effect of unequal path lengths by using an anisotropicdiffuser, which passes more light in one direction than in otherdirections.

[0100] As indicated above, the privacy screens of the invention may beused as overlays for video displays, for example to restricteavesdropping with respect to a computer display. In addition, theprivacy screens of the invention may be used as window coverings inorder to achieve a variety of effects not possible with conventionalmechanical blinds. For example, the privacy screens of the inventionhave the additional advantage that the prisms or lenticular structuresthat make up the screen may be used to bend incoming light and improvethe view from the window and, if the view from the window does notinclude any scenes worth expanding, he entire view may be replaced byimages or graphics.

[0101] Having thus described a number of preferred embodiments of theinvention in sufficient detail to enable those skilled in the art tomake and use the invention, it will nevertheless be appreciated thatnumerous variations and modifications of the illustrated embodiment maybe made without departing from the spirit of the invention. For example,the illustrated microprism and lenticular sheet configurations arehardly exhaustive of all of the possible configurations for such sheets.Accordingly, it is intended that the invention not be limited by theabove description or accompanying drawings, but that it be definedsolely in accordance with the appended claims.

What is claimed is:
 1. A field-of-view controlling arrangement made upof a single microprism or lenticular sheet having at least two sets ofparallel planar surfaces that intersect to define portions of prisms orlenticular structures, and additional surfaces not included in said twosets of parallel planar surfaces, wherein at least portions of each saidsurface in said sets of intersecting parallel planar surfaces arearranged to attenuate light transmitted through the sheet, wherein saidadditional surfaces are transparent, and wherein said light-attenuatingportions of each of said surfaces in said sets of intersecting parallelplanar surfaces thereby define privacy zones on at least two sides of afield-of-view for images transmitted through the sheet.
 2. Afield-of-view controlling arrangement as claimed in claim 1, whereineach said surface in said sets of intersecting parallel surfaces isarranged to attenuate light over an entire extent of the surface.
 3. Afield-of-view controlling arrangement as claimed in claim 1, whereineach said surface in said sets of intersecting parallel surfaces isarranged to attenuate light over only a portion of the surface.
 4. Afield-of-view controlling arrangement as claimed in claim 1, whereinsaid intersecting parallel surfaces and said additional surfacesrespectively define alternating grooves of a microprism sheet.
 5. Afield-of-view controlling arrangement as claimed in claim 1, whereinsaid intersecting parallel surfaces define spaced-apart grooves of amicroprism or lenticular sheet, and wherein said additional surfacesextend between said grooves.
 6. A field-of-view controlling arrangementas claimed in claim 5, wherein said additional surfaces are planarsurfaces extending between said grooves.
 7. A field-of-view controllingarrangement as claimed in claim 1, wherein said additional surfacesdefine lenticular structures extending between said grooves.
 8. Afield-of-view controlling arrangement as claimed in claim 1, whereinsaid intersecting parallel surfaces and said additional surfacesrespectively define alternating grooves on opposite sides of amicroprism sheet.
 9. A field-of-view controlling arrangement as claimedin claim 1, wherein said intersecting parallel surfaces definespaced-apart grooves on opposite sides of a microprism or lenticularsheet, and wherein said additional surfaces extend between said grooves.10. A field-of-view controlling arrangement as claimed in claim 1,wherein said intersecting parallel surfaces include surfaces treated byprocesses selected from the group consisting of coating processes,delustering, chemical or laser etching, casting, and differentialpolishing of previously roughened surfaces.
 11. A field-of-viewcontrolling arrangement made up of a single lenticular sheet made up ofpolyhedral lenticular structures having at least two sets of parallelplanar surfaces that intersect to define portions of the lenticularstructures, and additional surfaces not included in said two sets ofparallel planar surfaces, wherein at least portions of each said surfacein said sets of intersecting parallel planar surfaces are arranged toattenuate light transmitted through the sheet, wherein said additionalsurfaces are transparent, and wherein said light-attenuating portions ofsaid at least one if said surfaces in said sets of intersecting parallelplanar surfaces thereby defines a privacy zone for images transmittedthrough the sheet.
 12. A field-of-view controlling arrangement asclaimed in claim 11, wherein each said surface in said sets ofintersecting parallel surfaces is arranged to attenuate light over anentire extent of the surface.
 13. A field-of-view controllingarrangement as claimed in claim 11 wherein said lenticular structuresare truncated tetrahedral structures arranged in staggered rows.
 14. Afield-of-view controlling arrangement as claimed in claim 11, whereinsaid lenticular structures are truncated tetrahedral structures arrangedin a grid pattern.
 15. A field-of-view controlling arrangement asclaimed in claim 11, wherein said lenticular structures are tetrahedralstructures arranged in staggered rows.
 16. A field-of-view controllingarrangement as claimed in claim 11, wherein said lenticular structuresare tetrahedral structures arranged in a grid pattern.
 17. Afield-of-view controlling arrangement as claimed in claim 11, whereinsaid lenticular structures are truncated hexahedral structures arrangedin a honeycomb pattern.
 18. A field-of-view controlling arrangement asclaimed in claim 11, wherein said lenticular structures are truncatedhexahedral structures arranged in a honeycomb pattern.
 19. Afield-of-view controlling arrangement as claimed in claim 11, whereinsaid lenticular structures are hexahedral structures arranged in ahoneycomb pattern.
 20. A field-of-view controlling arrangement asclaimed in claim 11, wherein said intersecting parallel surfaces includesurfaces treated by processes selected from the group consisting ofcoating processes, delustering, chemical or laser etching, casting anddifferential polishing of previously roughened surfaces.
 21. Afield-of-view controlling arrangement made up of a single lenticularsheet made up of frustoconical lenticular structures having a curvedsurface and additional surfaces not included in a set of said curvedsurfaces, wherein at least portions of each said curved surface in saidset of curved surfaces s arranged to attenuate light transmitted throughthe sheet, wherein said additional surfaces are transparent, and whereinsaid light-attenuating portions of said curved surfaces thereby define a360° privacy zone for images transmitted through the sheet.
 22. Afield-of-view controlling arrangement as claimed in claim 21, whereinsaid curved surface is treated by processes selected from the groupconsisting of coating processes, delustering, chemical or laser etching,casting, and differential polishing of previously roughened surfaces.23. A field-of-view controlling arrangement, comprising: a microprism orlenticular sheet including a diffusing agent in at least a portion ofthe sheet, and surfaces arranged so that light transmitted through thesheet along selected optical paths is attenuated before exiting thesheet through a first set of surfaces while light transmitted alongother optical paths is relatively unattenuated before exiting the sheetthrough a second set of surfaces oriented at a nonzero angle relative toeach of the surfaces in the first set of surfaces, thereby achieving afield-of-view controlling arrangement that restricts viewing of an imagefrom more than one side of the potential field-of-view.
 24. Afield-of-view controlling arrangement as claimed in claim 23, whereinsaid bulk diffuser is distributed throughout said sheet.
 25. Afield-of-view controlling arrangement as claimed in claim 23, whereinsaid bulk diffuser is concentrated on a light entrance side of saidsheet.
 26. A field-of-view controlling arrangement as claimed in claim23, wherein surfaces in said first set of surfaces define spaced-apartgrooves of a microprism or lenticular sheet, and wherein said surfacesin said second set of surfaces extend between said grooves.
 27. Afield-of-view controlling arrangement as claimed in claim 26, whereinsurfaces in said second set of surfaces are planar surfaces extendingbetween said grooves.
 28. A field-of-view controlling arrangement asclaimed in claim 26, wherein surfaces in said second set of surfacesdefine lenticular structures extending between said grooves.
 29. Afield-of-view controlling arrangement as claimed in claim 33, whereinsurfaces in said first set of surfaces define spaced-apart grooves onopposite sides of a microprism or lenticular sheet, and wherein surfacesin said second set of surfaces extend between said grooves.
 30. Afield-of-view controlling arrangement, comprising a transparent sheethaving a plurality of spaced apart grooves on at least one side of thesheet, wherein each surface of each of said grooves is arranged toattenuate light to thereby define privacy zones on at least two sides ofa field-of-view for images transmitted through the sheet.
 31. Afield-of-view controlling arrangement as claimed in claim 30, whereinsaid transparent surfaces extending between said grooves are planar. 32.A field-of-view controlling arrangement as claimed in claim 30, whereinsaid transparent surfaces extending between said grooves definelenticular structures.
 33. A field-of-view controlling arrangementsuitable for use as a window covering, comprising: a microprism orlenticular sheet including surfaces arranged so that light transmittedthrough the sheet along selected optical paths is attenuated beforeexiting the sheet through a first set of surfaces while lighttransmitted along other optical paths is relatively unattenuated beforeexiting the sheet through a second set of surfaces oriented at a nonzeroangle relative to each of the surfaces in first set of surfaces, whereinsad second set of surfaces is arranged to expand a scene visible throughthe window.